Apple is now suggesting that it's a hardware problem (which seems rather coincidental to me... I had a phone that worked just fine before the update).
I compare hardware failures to flat tires. They can happen anytime, for any reason, or for no apparent reason. Sometimes you take your car into the shop and they find a nail and pull it out and patch the hole and you're fine. Maybe it's just a bead re-seal. But sometimes it's just flat for no apparent reason. Or there's a hole and they have no idea what caused it or what you could have done to avoid it happening again.
And just like a tire, you can get
another flat on the way home just a few minutes after getting it fixed, if you find another nail or the replacement tire is defective or was installed wrong, or damaged during installation. Just because it was fine five minutes ago does not mean it has any right to still be fine now. Hardware can go from working perfectly to not working with no warning. Put aside "But it was working just an hour ago!" and accept that it may have failed 5 minutes ago.
Software changes are a whole new wrench. They cause data to be moved around in the hardware, and a bit of code that rarely or never gets run by you in the OS gets displaced by something critical to the stability of the phone. No amount of restores will fix that. It was broke, it still IS broke, it's just that now you're being affected by the problem (of bad cells in the flash memory) whereas before you weren't. If you wait a month and do a restore on a newer build of the OS, something else may move into the bad cell and heaven only knows what sort of different symptoms you'll see. Or maybe it will "appear to fix itself" as now the bluetooth headphones code is buggered but you don't use that feature. So *shrug* it must be fixed by that update! well... sorta.... but not really. Another update available? Do you dare to spin the wheel?
